#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
int main()
{
    int n = 0;
    scanf("%d", &n);
    int sum = 0;
    while (n)
    {
        sum += n % 10;
        n /= 10;
    }
    printf("%d\n", sum);

    return 0;
}